<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>demo8</title>
	<style type="text/css">
	#a1{
		border: 10px solid #C3C3C3;
		padding: 10px;
		margin: 40px;
		width: 200px;
		height: 200px;
		float: left;
		background-color: red;
	}
	.a2{
		border: 10px solid blue;
		padding: 10px;
		margin: 12px;
		width: 200px;
		height: 200px;
		float: left;
	}
	</style>
</head>
<body>
	<div id="a1">aaaaaaaaaaaaa</div>
	<div class="a2">bbbbbbbbbbbbb</div>
</body>
</html>